The two bags you posted are good options. Kelty also has some good options in that range.

Here are my thoughts on scout sleeping bags. To start, I am a scout master who likes to backpack and take scouts backpacking. I also know that backpacking makes up a tiny percentage of scout campouts. The majority of the time, your scout won't be backpacking. So, here is my best, better, and good suggestions.

Best-
Buy a dedicated backpacking sleeping bag in the 20F range.
Buy a HEAVY duty canvas covered bag in the 20F range.
Buy a winter bag.
The majority of the time, he will use the canvas bag, like 95% of the time. It should also withstand the destruction that he and other boys will do to it.

Better- (this is what I did for my boys)
Buy an MSS sleep system (this is the army's current issue setup). It comes with two sleeping bags that nest inside each other, and a gortex bivy.
Buy a dedicated backpacking sleeping bag.
The army system is great for scouts. You can buy them for around $100 all over the place online. In the winter, you bring the whole system. In fall and spring, you only bring the bivy and heavy black bag. In summer, the bivy and light green bag. You save the nice backpacking sleeping bag for when you are backpacking, and he has a bivy for when the tent he is in (during any campout) leaks.

Good-
Buy the army MSS sleep system and a poncho liner.
When he backpacks, he only takes the green bag and the poncho liner. And, depending on where/when he backpacks and his other clothing...he can probably skip the poncho liner.

As a scoutmaster, I have 3 sleeping bags for myself. One backpacking quilt that I made that is good to below 20F, and weighs close to 2lbs. One old army mummy bag that is canvas covered and good to below 20F, and one mummy bag that weighs around 8 lbs, and is good to -25F. 95% of the time, I use the old army bag. I do plan to replace my winter bag with either an MSS system, or a Wiggy's -25F bag. I also hope to replace the homemade quilt with another homemade quilt, but filled with down.